If you want to do anything malicious, except for killing the device, you nead power supply for your tool.
The USB A-B, A-mini, A-micro, A-Olympus, A-lightning cables are only conductors. Whole comunication is done by USB dirver in your computer and the device. In the cable, there can be resistors and passive filters only.
The cable, and hypothetical TLA device, are designed to operate with 5 VDC power supply and digital signals.
If you connect 20 VAC between any pair of pins, icluding shielding, and something blows up, the cable was TLA-modified and it drew power from USB.Building something capable to fully operate with power supply ranging from 0-1 kV, both AC and DC is impossible.
If you are suspicious of self-powered TLA-device, you can use good ol' X-Ray. Buy Photographic paper, keep it in dark envelope, put the USB ports on it and place uranium ore ontop of it. Develop the photograph next day and you will get X-Ray shadow of the interior. If it is TLA-modified, you will see extra circuitry.
If you think it is still not enough, you can apply really strong and dynamic magnetic field to it. EMP (nuke) or magnetic resonance (NMR) are capable of such magnetic shocks. Every circuit will induce enough current to fry itself. If the cable survives, you are sure, it wasn't TLA-modified.
In the real world, device, that is capable of anything malicious and is that small costs a lot of effort (= money) to be used as a random device. There is no way the atacker has ide wht are you about to do with the cable - they are Universal (Serial Bus cables) -, you can use them to charge your bike light, for example.
Therefore thay are useful for targetted attack only. In that case, TLA will more likely replace cable you already use with the TLA-enhanced one. If you are paranoid enough, using randomly bought cheap USB cables is the way to be sure, you are not TLA-monitored via USB plug listen-and-report technique. The procedure is: Buy, use, dispose. No re-use, no storage.
Using cheap USB cables is, with respect to TLA-infestation only, completely safe.